Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
Technol Cancer Res Treat. 2024 Jan-Dec;23:15330338241272038. doi: 10.1177/15330338241272038.
This study aims to investigate the influence of the magnetic field on treatment plan quality using typical phantom test cases, which encompass a circle target test case, AAPM TG119 test cases (prostate, head-and-neck, C-shape, multi-target test cases), and a lung test case.
For the typical phantom test cases, two plans were formulated. The first plan underwent optimization in the presence of a 1.5 Tesla magnetic field (1.5 T plan). The second plan was re-optimized without a magnetic field (0 T plan), utilizing the same optimization conditions as the first plan. The two plans were compared based on various parameters, including con-formity index (CI), homogeneity index (HI), fit index (FI) and dose coverage of the planning target volume (PTV), dose delivered to organs at risk (OARs) and normal tissue (NT), monitor unit (MU). A plan-quality metric (PQM) scoring procedure was employed. For the 1.5 T plans, dose verifications were performed using an MR-compatible ArcCHECK phantom.
A smaller dose influence of the magnetic field was found for the circle target, prostate, head-and-neck, and C-shape test cases, compared with the multi-target and lung test cases. In the multi-target test case, the significant dose influence was on the inferior PTV, followed by the superior PTV. There was a relatively large dose influence on the PTV and OARs for lung test case. No statistically significant differences in PQM and MUs were observed. For the 1.5 T plans, gamma passing rates were all higher than 95% with criteria of 2 mm/3% and 2 mm/2%.
The presence of a 1.5 T magnetic field had a relatively large impact on dose parameters in the multi-target and lung test cases compared with other test cases. However, there were no significant influences on the plan-quality metric, MU and dose accuracy for all test cases.
本研究旨在通过典型体模测试案例，包括圆形靶测试案例、AAPM TG119 测试案例（前列腺、头颈部、C 形、多靶测试案例）和肺测试案例，研究磁场对治疗计划质量的影响。
对于典型体模测试案例，制定了两个计划。第一个计划在 1.5T 磁场下进行优化（1.5T 计划）。第二个计划在没有磁场的情况下重新优化（0T 计划），使用与第一个计划相同的优化条件。根据各种参数比较两个计划，包括适形指数（CI）、均匀性指数（HI）、拟合指数（FI）和计划靶区（PTV）的剂量覆盖率、危及器官（OAR）和正常组织（NT）的剂量、监测单位（MU）。采用计划质量指标（PQM）评分程序。对于 1.5T 计划，使用 MR 兼容的 ArcCHECK 体模进行剂量验证。
与多靶和肺测试案例相比，圆形靶、前列腺、头颈部和 C 形测试案例的磁场剂量影响较小。在多靶测试案例中，下 PTV 的剂量影响显著，其次是上 PTV。肺测试案例中 PTV 和 OAR 的剂量影响较大。PQM 和 MU 无统计学差异。对于 1.5T 计划，2mm/3%和 2mm/2%的标准下，伽马通过率均高于 95%。
与其他测试案例相比，1.5T 磁场对多靶和肺测试案例的剂量参数有较大影响。然而，对于所有测试案例，计划质量指标、MU 和剂量准确性均无显著影响。
